| 摘要 |
A microphone unit comprises first and second microphones and a delay element. When sound is input to the first and second microphones, the delay element delays an output signal of the first microphone so as to detect the sound by a difference signal between the output signal of the first microphone and an output signal of the second microphone. The delay element delays the output signal of the first microphone so as to satisfy relation 0.76≦̸D/&Dgr;r≦̸2.0 where D is amount of delay for the output signal of the first microphone while &Dgr;r is distance between the first and second microphones. The relation D/&Dgr;r≦̸2.0 can reduce far-field noise, while the relation 0.76≦̸D/&Dgr;r can increase the detection sensitivity to sound emitted from a null point.
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